How does DOTA judge whether others are black or not?

Very simple, by cooperation, especially in the continuity of some skills. The communication between passers-by and teammates is very simple, so the skill coordination and position will be so uneven, or it will be a very fixed formula.

Another is to look at the location. If many people often arrest people together or arrest people soon, it is often a black shop.

Mainly speaking, the black shop is a team, and passers-by are fighting on their own. You can see the difference if you distinguish it carefully.

Of course, it does not rule out that the opposite side is full of experts or most of them are experts. After all, the cooperation mode in dota is limited. If the strength reaches a certain level, even passers-by will not be worse than ordinary black shops (but certainly not as strong as black shops with the same strength). However, in a passer-by war, the opponents are random, and the possibility of misjudging a black shop is very small. Only when three or more opponents are obviously stronger than their own strength will there be a situation of misjudging black shops.